The present invention generally relates to the field of automotive systems, and particularly to power window systems.
In a power window system, when current to the motor that causes the window to move is reversed, inertia will cause the motor to continue to move in the original direction for a brief period of time for a certain distance, typically up to one armature revolution for a duration of approximately 10 milliseconds. Precise resolution of the position of the window by the power window""s control system requires knowledge of when the motor reversal actually occurs, and not just the point in time at which the reverse direction signal was applied to the motor. Furthermore, knowledge of the inertia of the window dampers and other mechanical aspects of the power window regulator system are required to obtain a precise window position solution. Thus, it would be highly desirable to be able to determine the motor rotor position in a power window system with a higher level of precision.
The present invention is directed to a method and apparatus for determining motor rotation in a power window system or the like. The position of the rotor is determined by monitoring the current flowing in the motor and calculating the motor equation solved for counter electromotive force. The time at which the value of the counter electromotive force changes sign corresponds to the time at which the rotor changes direction in response to a new motor control input such that the position of the rotor may be determined with a higher level of precision.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and together with the general description, serve to explain the principles of the invention.